Despite the ongoing efforts in modern society to recycle, the efforts towards recycling tires has curiously remained a difficult problem to solve. This problems persists today because the technology for manufacturing new tires--radial tire technology--has virtually made obsolete the technology for recapping tires. As a result, the industry for recapping tires has all but vanished in recent years. In its place, huge mountains of spent tires are being stockpiled at dump sites where they constitute a waste of space, an ongoing eye sore and danger should they be ignited. Reports occur of mountains of spent tires having caught fire. These fires often burn unchecked until all of the stockpiled tires have been consumed, an event that can takes months, if not years. During the uncontrolled burning, the atmosphere is polluted and the ground contaminated by rivers of molten petroleum products released from the burning tires. Damages are incalculable.
Once, recapping tire casings was a thriving, established industry. The industry still survives today, if only for applications directed substantially toward industrial and commercial vehicle tires. Even so, the industry still suffers from a wide variety of problems. The most prevalent problem is the dislodgment of the annular band defining the recap from the spent tire casing. The primary reason that the recap band becomes disassociated from the tire casing is poor adhesion. High vehicular speeds create extreme heat which causes separation along the interface between the tire casing and recap band. Variances in the recap band shape exacerbate this problem. This separation contributes to the frequent failure of recapped tires. This failure has been the principal reason most retail consumers are biased against retreads. Yet, economics still support the retread business for commercial and industrial tires (because of the high cost of these tires). Thus, tire sales to commercial fleet companies still remain commonplace.
Until the advent of the radial tire, the predominate method for recapping spent tire casings was the hot capping method. With this method, a spent tire casing (also called a carcass or tire carcass) was prepared, and then a recap band of uncured rubber was introduced along the outside periphery of the tire casing. The tire casing was stretched and under high temperature and pressure, typically 160 psi and 305.degree. F.; the band of uncured rubber was adhered, as it cured, to the tire casing creating a sturdy and robust retread by creating a fairly strong bond between the new and the old rubber. However, with radial tires, traditional methods for recapping could not be used. Although the new radial tire technology provided a much stronger tire initially, when the radial tire wore out, the prospects for retread were dismal. The known hot capping technology could not be used for radial tires. The primary difficulty with retreading of radial tires is that a radial tire cannot be stretched. The radial cords imbedded in the tire rubber prevent the stretching of the tire casing--a necessary and integral procedure for the manufacturing of retreads using the prior hot capping method.
Because of the inability to stretch the spent radial tire casings under high temperature and pressure, alternative procedures were developed without stretching, using lower temperatures and pressures. The alternative procedures were inferior. The alternative procedures provided for application of the uncured rubber to the spent radial tire at much lower temperatures and pressures. Typically, heated, highly pressurized air, or gas, was used to provide both the heat and pressure needed for the process. Curing times were longer, which substantially lengthened manufacturing time. Moreover, without high temperatures and pressures, the strength of the recap rubber was compromised resulting in an inability to obtain the stronger recap band of previous retreads. As a consequence, the life of the retread tire was shortened, and its economic value diminished. Further, because of the use of highly pressurized air, safety risks to manufacturing process operators were substantial. When the pressurized air system failed during the manufacturing process, the instantaneous pneumatic expansion--a violent explosion--could, and did, cause severe injury and death.
Cold capping of retread tires was developed as an alternative to the hot capping method. With cold capping, the recap band was precured prior to attaching it to the tire casing. Typically, the recap band was cured at the desirable higher temperatures and pressures as a flat piece of rubber. The precured recap band was later attached with adhesive to the perimeter of the tire casing. Although the precured recap band had the superior qualities of the hot cap recap band manufactured using high pressure and temperature, because precured rubber has a "memory" of the shape in which it was originally cured, the precured flat recap band tried to return to its original shape after it was adhered to the tire casing. That is, with cold capping, the memory of the precured flat recap band resists the curved shape of the tire casing perimeter, fighting the adhesive which attaches it to the tire casing. Because the memory of the recap band opposed the adhesive, the life of the adhesive was diminished. Yet curing the recap band in a curved shape to match the tire casing perimeter is so costly as to make it an unattractive and commercially undesirable alternative to the precured flat recap band. The aesthetic of the retread manufactured by the cold capping process also diminished it's commercial success with the retail consumer as the cold cap retread was considered unattractive.
With the radial tire causing the retread manufactured by the hot capping process to be of substantially diminished quality, and the retread manufactured by the cold capping process to also be undesirable, the retread business has sharply fallen off in recent years. It is only in the commercial and industrial vehicle market, where new tire costs is substantially higher, that the retread business has managed to survive. The retail consumer tires of today are just not retread--instead spent tires are retired to the unsightly, and ever expanding, stockpiles of local waste sites.
The following documents further reflect the state of the art of which applicant is aware and have been included herewith to discharge applicant's acknowledged duty to disclose relevant prior art. It is stipulated, however, that none of the prior art teach singly nor render obvious when considered in any conceivable combination the nexus of the instant invention as set forth hereinafter and as especially claimed.
______________________________________ INVENTOR ISSUE DATE U.S. PAT. NO. ______________________________________ Fetter October 31, 1933 1,932,692 Freeman December 29, 1936 2,066,265 Leguillon, et al. October 2, 1951 2,569,935 Ostling November 22, 1955 2,724,425 White May 14, 1957 2,791,805 White May 27, 1958 2,835,921 Barefoot October 14, 1958 2,855,629 Pfeiffer February 6, 1962 3,020,190 Keefe October 4, 1966 3,276,930 Ireland, et al. November 6, 1973 3,770,858 Fredericks, et al. February 19, 1974 3,793,420 Barefoot June 11, 1974 3,816,217 MacMillan November 12, 1974 3,847,631 Barefoot December 10, 1974 3,853,666 Foegelle July 13, 1976 3,969,179 Batchelor, et al. March 21, 1978 4,080,230 Baatz May 23, 1978 4,090,901 Cole, et al. June 27, 1978 4,097,565 Logan August 23, 1983 4,400,342 Mattson May 1, 1984 4,446,093 Mattson, et al. December 25, 1984 4,490,325 Fike, et al. March 11, 1986 4,575,438 Greenwood, et al. August 5, 1986 4,604,256 Greenwood, et al. December 29, 1987 4,715,577 Mattson March 28, 1989 4,816,198 Seiberling July 25, 1989 4,851,063 Majerus August 15, 1989 4,857,122 Lindsay, et al. October 8, 1991 5,055,148 Trethowan July 7, 1992 5,127,811 Lindsay, et al. September 29, 1992 5,151,148 ______________________________________
The patent to Baatz teaches the use of a recapping method for tires using a flat precured recap band. The tire to be recapped is placed within an envelope with the precured recap band thereabout. A hose runs from inside the envelope to outside the tank in which the tire is placed. Hot water is pumped into the airtight tank. The rising air and water pressure force the air out of the envelope and press the envelope firmly against the recapped tire to hold the recap band securely in place.
The two patents to Lindsay, et al. (U.S. Pat. Nos. 5,055,148 and 5,151,148) teach the use of a method and system for retreading spent tires with precured treads utilizing time and temperature in conjunction with an envelope pressure system. A precured rubber tread is applied to a tire casing having a cushion gum disposed therebetween. An envelope system is placed over the tread/tire casing and this assembly is placed within a pressure chamber. Heat and fluid pressure are then supplied to the chamber. Fluid pressure is then supplied to the chamber after both a predetermined length of time and after a predetermined temperature of the chamber has been reached.
The patent to Seiberling teaches the use of a radiation cure of tire plies. In a continuous operation, steam or hot water is led into the mold through a pipe and provides sufficient pressure within the tire to force it against the mold to groove the tread and form any desired identification and indicia marks desired on the tire surface. The tire is cured at usual temperatures, and steam or hot water is used in the usual manner, but without an air bag or bladder.
The patent to Foegelle teaches the use of a curing apparatus which may be used for vulcanizing a pre-cured tread onto a suitably prepared tire casing. The apparatus provides a mold defining a chamber in which the tire casing and adhesively attached pre-cured tread are placed and includes means for establishing pressurized fluid, such as steam or air, within the interior of the tire casing and pressurized fluid, such as steam, in the annular space between the casing and the inside peripheral surface of the chamber.
The patent to Trethowan teaches the use of a bladderless tire mold press for tires, including lower and upper platens and a mechanism for moving the platens relatively toward one another from an open position to a closed molding position. Each of the platens further includes a mechanism for molding tire beads. Note column 4, from line 26. The curing medium may be steam or hot water. The effect of this is to expand the green tire so as to properly engage with the various molds surrounding it.
The patent to Majerus teaches the use of a process for injection molding tire treads. Note the discussion of operation starting at column 4, line 16 through column 5, line 17, which utilizes a first low pressure on the interior of the tire casing to position the tire casing until the injection of tread material is complete and then uses a second higher pressure for curing.
The remaining citations not specifically discussed diverge even further from the focal point of patentable novelty as set forth hereinbelow.